It can be unmistakably identified by the harsh engine note, due to high tip speed of the air screw

It can be unmistakably identified by the harsh engine note, due to high tip speed of the air screw.
(a) What does ‘it’ refer to here?
(b) Which feature can be identified here?
© Which word in the extract is a synonym of ‘jarring’?

(a) ‘It’ here refers to the North American Harvard Trainer Aircraft.
(b) The feature which can be identified here is the harsh engine note because of high tip speed of the airscrew.
© The word is ‘harsh’.